Welcome to the Newbie crashing club Emily.
I havent been lying in my past posts when I said I seemed to spend more time off my mountain bike than on it. Keep riding and watch your experienced mountain biking friends ride any parts you find difficult. I did this when I went mountain biking with SadieKate and it was amazing I didnt fall off once. It really helped having someone more experienced give tips. Riding sections of the trail over and over can help nail the harder parts.

Sending staying upright wishes your way.

Trek - Vertically Challenged mountain biker - hawk

PS I think mountain biking is a combination of terror and exhilaration.